Multi-propeller aerial vehicles (e.g., quad-copters, octo-copters) are becoming more common. All such vehicles require a body configuration that will support the separation of the multiple propellers, the control components, the power supply (e.g., battery), etc.
FIG. 1 illustrates examples of common multi-copter design types. The typical airframe configurations today consist of “X”, “H” and “V” types (FIG. 1) if the UAV has 4 rotors (quad copter). A smaller number of vehicles have 3 (tri-copter), 6 (hex copter) or 8 (octocopter) rotors. Regardless of the number of rotors or configuration type, the designs tend to follow a similar pattern—that is, they consist of a center “plate”, with arms projecting out from the center plate that have electric brushless motors mounted at the ends of them. The consumer-oriented vehicles increasingly are manufacturing this configuration (the majority being quad copters, with four rotors) as one body, merging the arms into the center plate in a more curved, visually appealing manner, or encasing the center plate and arms in an outer plastic body. This can be done because the vehicles are small enough that such a design does not detract too much from flight time or cause excessive frame flexing in the air since the motors (with small propellers) are relatively close to the center of the vehicle. But even in these products, the basic design remains unchanged—the center area houses flight electronics (autopilot, remote control receiver, GPS receiver, battery, etc.) with arms protruding out to the motors. The larger multi-copters, weighing 10 pounds or more, are almost exclusively designed using a center plate and rectangular or tubular arms made of lightweight metals or carbon fiber extending out to the motors.
Multi-copter designs are compromised in several areas:
(1) First, with the exception of a handful of very small micro copters, the propeller blades (rotors) are not enclosed. That is, they spin freely, enabling them to come into contact with people, tree branches, and other property (including buildings and vehicles), posing great danger to people and risking damage to property, and almost certainly causing significant damage to the multi-copter itself. Larger multi-copters, with 12 inch+ propellers spinning at RPMs in excess of 10,000, easily pose life-threatening injuries to people.
(2) For the majority of multi-copters, with motors attached to arms protruding from a center plate, the entire weight of the vehicle, as well as inertial forces from the motors and atmospheric environment, has to be carried/absorbed through these specific joints, requiring them to be reinforced. Still, because of weight considerations, there is always a compromise between strength and weight that leaves the arms vulnerable to bending and/or breaking depending on the materials used to manufacture them.
(3) Mounting space for vehicle electronics is mostly limited to the center part of the vehicle due to the lack of available flat surfaces that are sufficiently far from the motors. Not only does this limit the number of devices that can be attached to the vehicle, but also, and most importantly, existing designs make it difficult to separate electronic equipment, particularly radio frequency (RF) electronics, such as remote control, data, and audio/video transmitters and receivers, far enough from one another to consistently prevent interference. This interference can cause loss of vehicle control (or at a minimum reduce remote control, video or wireless data range) or other functions from operating as intended. For example, some vehicles cannot operate a Wi-Fi camera on board because it can interfere with remote control signals that use the same frequency range or reduce effectiveness of the GPS antenna, thereby diminishing or making impossible the ability for the vehicle to determine its geographic coordinates.
(4) Landing gears/pads tend to be thin and tubular, projecting down from the arms or center body. As they serve only one function, manufacturers tend to engineer them to a minimum strength to limit deadweight of a component that is only used at the beginning and end of a flight. As a result, like the arms, they can easily break and/or bend.
(5) For the most part, existing multi-copters are weather-sensitive. Smaller products lack the stability required to tolerate windy flight conditions. Very few are capable of flying in rain or snow without risking serious damage to the electric motors, motor controllers or other vehicle electronics.
Accordingly, it would be desirable to provide an unmanned aerial vehicle that addresses at least some of the problems identified above.